1. Field of the Invention
The present invention relates to a glass substrate and, more particularly, to a glass substrate to be used for a display apparatus.
2. Description of the Related Art
A glass substrate for a display apparatus according to the related art has been produced by the following method. FIG. 2 shows a method called a float method.
First, a glass material 204 is melted in a melting furnace 201 and is fed into a float bath 202. The float bath 202 contains a molten tin 205 and the glass material 204 spreads thin on the molten tin 205. As glass passes through the float bath 202, the glass is formed to have a predetermined width and a predetermined thickness. Next, glass 206 is pulled toward a cooling furnace 203 from the glass-outlet side end of the float bath 202. The cooling furnace 203 has a length of several tens of meters, so that as the glass passes through the furnace, the glass is cooled down.
The glass formed here is called a mother glass or glass ribbon. The mother glass has a short side ranging from several tens of centimeters to several meters and is drawn into a band shape.
The mother glass often has a rectangular shape. In case where the mother glass has a rectangular shape, longer two of the four sides of the mother glass are called long sides and the other two sides shorter than the long sides are called short sides.
After cooled, the mother glass is cut and undergoes steps, such as surface polishing, cleaning and inspection. Thereafter, the resultant mother glasses will be distributed to companies that need the mother glasses, such as display apparatus manufacturing companies.
Glass substrates for display apparatuses of the related art have different glass size from each other in accordance with demand of respective display apparatus manufacturing company or factory. Therefore, a glass manufacturing company cuts a mother glass in accordance with the demands of each demander.
Each display apparatus manufacturing company has demanded the glass manufacturing company to supply glasses of the desired sizes in accordance with display apparatuses to be manufactured.
In case of manufacturing 15-inch display apparatuses, for example, a glass substrate of 550 mm×650 mm, a size that provides four panels, has been used.
As apparent from the foregoing description, sizes of glass substrates for display apparatuses, which are prepared by cutting a mother glass, differ from one display apparatus manufacturing company or factory to another. Therefore, it is not always the case where cutting glass substrates away from a mother glass is carried out efficiently and mother glasses are not used efficiently. One example of such an inefficient usage is illustrated in FIG. 3. FIG. 3 shows a case where glass substrates for 550 mm×650 mm display apparatuses are cut away from a mother glass having short sides of 1 m. In this case, the mother glass includes a lot of areas that are not actually used. This results in a wasteful use of the mother glass.